Ambopteryx had a long wristbone that likely supported leathery membranes, allowing it to glide between trees.

Two years ago, a farmer from Wubaiding Village, in northeastern China, came across a beautiful fossil. The only animal fossils that had ever been found at this site were a pair of salamanders, but when Min Wang from the Chinese Academy of Sciences saw the new specimen, he was sure it was a dinosaur.

Studying the beautifully preserved and nigh-complete skeleton, Wang took note of the creature’s sparrow-size body, the quill-like feathers on its neck, and its stubby tail. But when he looked more closely at the left arm, he saw a thin bone coming down from its wrist—a rod as long as the entire forearm, but not jointed like a finger. “I shouted, and my heartbeat elevated,” he says.